1. Field of the Invention
The present invention relates to a wiring circuit board used for, for example, a flexure of a head suspension and a method of manufacturing the same.
2. Description of the Related Art
A hard disk drive (HDD) has a hard disk and a head suspension for supporting a magnetic head (functional part). The magnetic head is connected to wiring of the head suspension to read and write data from and to the hard disk.
Recently, it is required for a HDD higher recording density and higher reliability. For this, additional components such as a heater for controlling a flying height and a head disk interface (HDI) sensor may be incorporated into a magnetic head in addition to usual read/write elements. Further, components for energy assisted recording and the like are considered to be incorporated into the magnetic head. With this, many magnetic heads have ten or more terminals including ground terminals.
In current HDDs, a minute slider so-called “Femto slider” having a width of mere 0.7 mm is used for a magnetic head. To connect the magnetic head to wiring of a head suspension, the ten or more terminals arranged within the width of 0.7 mm of the slider have to be joined to the respective terminals of the wiring of the head suspension without short circuit.
Such a connection between terminals of a slider and a head suspension is often carried out by reflow soldering with the use of micro solder balls as disclosed in U.S. Pat. No. 7,239,484B2, U.S. Pat. No. 7,984,545B2, U.S. Pat. No. 8,213,121B2, U.S. Pat. No. 8,295,011B2, and U.S. Pat. No. 8,295,012B1.
FIGS. 17A and 17B are schematic sectional views illustrating connections established between terminals in a head of a flexure by reflow soldering with the use of a micro solder ball in which FIG. 17A is a relative large connection and FIG. 17B is a relative small connection.
As illustrated in FIGS. 17A and 17B, a micro solder ball 109 is put in a trough part defined between a terminal 103 of a slider 101 and a terminal 107 of a flexure 105 and thereafter is reflowed to form a connection or fillet 111 and bond or solder the terminals 103 and 107 together.
If the number of the terminals 107 is relatively small, for example, four for the read/write elements, the terminals 103 and 107 are relatively large and accordingly the solder ball 109 is also relatively large in size so that the fillet 111 is formed to be thick enough for the connection as illustrated in FIG. 17A.
If the number of the terminals 107 is relatively large, for example, ten for adapting a multi-function slider, however, the terminals 103 and 107 are relatively small and accordingly the solder ball 109 is also relatively small in size so that the fillet 111 is formed to be thin not enough for the connection as illustrated in FIG. 17B. This causes proportion of a defective connection between the terminals 103 and 107 to be increased.
Such a defective connection is also caused on terminals of a tail part that are joined to terminals of a main flexible circuit board using solder balls.
Further, a recent head suspension may have piezoelectric elements that are connected to a flexure in order to minutely position a magnetic head. In this case, conductive paste is used for a connection between terminals of the flexure and the piezoelectric elements. If the amount of the conductive paste is decreased, a defective connection is caused similar to the above.
These problems are caused by level of the terminal as the functional part in a thickness direction. Such a problem is also caused in an aerial wiring part of a flexure in which a wiring layer passes over an opening formed through a metal support layer and a reference hole formed through the wiring layer and used for image processing.
In the aerial wiring part, it is difficult to simultaneously accomplish thinning of an electric insulating layer and flattening of the wiring layer and stabilize rigidity of the flexure.
In the reference hole, a peripheral part of the reference hole is dropped toward the electric insulating layer to have a bent shape and an edge unnecessary for the image processing. This causes misrecognition in the image processing.
To cope with such a problem, there is a technique to correct level of a terminal in a thickness direction as disclosed in JP 2005-251262 A.
FIGS. 18A and 18B are sectional views illustrating terminals defining a reduced gap therebetween by bending a flexure including a metal support layer in which FIG. 18A is of a raised terminal and FIG. 18B is of a inclined terminal.
In FIGS. 18A and 18B, the terminal 107 is bent by machining operation together with the metal support layer 113 so as to change the position of the terminal 107 relative to the terminal 103 of the slider 101 and put the terminal 107 closer to the terminal 103. With this, the gap between the terminals 103 and 107 is reduced to form a thick fillet enough for the connection.
The machining operation conducted to the flexure including the metal support layer 113, however, tends to cause variation in bent shape such as bent angle. This results in variation in thickness of a fillet among products to deteriorate quality of solder bonding.
If such machining operation is conducted to the aerial wiring part, the reference hole, its periphery or the like, it results in variation in bent shape and deterioration of quality of the aerial wiring part or the like.